STRUCTURE OF (20R)-5-ALPHA-PREGNANO[3,4-C][1,2,5]OXADIAZOL-20-OL (HS1011)

C21H32N2O2, M(r) = 344, orthorhombic, P2(1)2(1)2(1), a = 7.353 (1), b = 10.153 (1), c = 25.324 (3) angstrom, V = 1891 angstrom 3, Z = 4, D(x) = 1.21 g cm-3, lambda(Cu K-alpha) = 1.5418 angstrom, mu = 5.30 cm-1, F(000) = 752, room temperature, R = 0.054 for 2968 observed reflections. All rings of the steroid skeleton are trans connected. Ring A is strained and rings C and D are in chair conformations. Ring D has an intermediate envelope-half-chair conformation. The oxadiazole ring is planar. The methyl and hydroxyl side groups linked through C(18) to the steroid skeleton at C(17) are equatorial and axial respectively.